There have been known fiber application machines, commonly designated by fiber placement machines, for applying a wide strip, formed of a plurality of ribbon-type resin impregnated flat fibers, particularly carbon fibers impregnated with a thermoplastic or thermosetting resin, onto a male or female mold. These machines, such as described in patent document WO2006/092514 comprise a system for displacing a fiber application head, a fiber storage, and a fiber conveyor for conveying the fiber from the fiber storage to the application head.
Typically, the fiber application head, also called fiber placement head, comprises an application roller intended to come into contact against the mold in order to apply the strip, and a guiding system for guiding the fibers on said application roller.
The displacement system allows for the displacement of the application head according to at least three directions perpendicular to one another. The displacement system may be constituted by a standard six axis robot-type polyarticulated arm, arranged on the floor or mounted over a linear axis, with an end wrist to which the application head is attached, or a gantry-type Cartesian-coordinate robot provided with an end wrist carrying the application head. In the case of fibers packaged in the form of spools, the fiber storage typically comprise a creel. The creel is arranged on the floor, in the case of a stationary six axis standard robot, for example, or may be mounted on a member of the displacement system, on one of the carriages of the Cartesian-coordinate robot or on a follower-carriage sliding on the linear axis of the six axis robot for example.
Such as described in the aforementioned patent document, the fiber conveyor is advantageously formed of flexible tubes connecting the fiber storage to the application head, each flexible tube being able to receive a fiber in its internal passage. The flexible tubes are attached by their ends to the application head and the fiber storage, respectively, through an upstream and downstream fixing system and have sufficient length and flexibility so as not to limit the movements of the head displacement system.
Owing to the stickiness of the pre-impregnated fibers, the application head and the flexible tubes may have a tendency to clog up.
In patent document FR 2 912 953 filed by the present applicant, it has been proposed to inject compressed air in each tube in order to fluidize the transport of fibers. With regard to pre-impregnated fibers of which stickiness decreases with temperature, compressed air is advantageously cooled so as to limit the clogging of the tubes as well as the friction of fibers inside the tubes. Owing to the low cross-section of the tubes, the compressed air injection system is provided so as it directly injects compressed air within each tube. Such a compressed air injection system proves to be complex, and the cooling of the compressed air proves to be also difficult to implement and sometimes not sufficient.